The Effects of the Local Environment and Stellar Mass on Galaxy Quenching to z ~ 3

Abstract

We study the effects of the local environment and stellar mass on galaxy properties using a mass complete sample of quiescent and star-forming systems in the COSMOS field at z ≾ 3. We show that at z ≾ 1 the median star formation rate (SFR) and specific SFR (sSFR) of all galaxies depend on the environment, but they become independent of the environment at z ≳ 1. However, we find that only for star-forming galaxies, the median SFR and sSFR are similar in different environments regardless of redshift and stellar mass. We find that the quiescent fraction depends on the environment at z ≾ 1 and on stellar mass out to z ~ 3. We show that at z ≾ 1 galaxies become quiescent faster in denser environments and that the overall environmental quenching efficiency increases with cosmic time. Environmental and mass quenching processes depend on each other. At z ≾ 1 denser environments more efficiently quench galaxies with higher masses (log(M/M_☉) ≳ 10.7), possibly due to a higher merger rate of massive galaxies in denser environments. We also show that mass quenching is more efficient in denser regions. We show that the overall mass quenching efficiency (є_(mass) for more massive galaxies (log(M/M_☉) ≳ 10.2) rises with cosmic time until z ~ 1 and then flattens out. However, for less massive galaxies, the rise in є_(mass) continues to the present time. Our results suggest that environmental quenching is only relevant at z ≾ 1 and is likely a fast process, whereas mass quenching is the dominant mechanism at z ≳ 1 with a possible stellar feedback physics.

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